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Friday, 8 March 2013

WDYTYA Live Day 3 Part 2: The new ancient root of the Y-tree

Sunday is always the quietest day at WDYTYA and in a lull at the end of the day I took the opportunity to listen to a fascinating talk by Dr Michael Hammer from the University of Arizona on "DNA and our ancestral origins". The talk began with an explanation of the two different models of human evolution - the Out of Africa replacement model and the multiregional model. Hammer discussed the important work of Svaante Pääbo from the Max Planck Institute who has sequenced the Neanderthal and Denisovan genomes. All non-Africans carry traces of Neanderthal DNA. Small percentages of Denisovan DNA are found today only in populations in Melanesia. I have been surprised to see that most of the people who have taken the new Geno 2.0 test from the Genographic Project have reported receiving small percentages of Denisovan DNA, despite having ancestors who lived in Europe and not Melanesia. These figures can be seen in this thread on the Genealogy DNA mailing list. I asked Michael Hammer why this should be the case, and he suggested that these results must surely be in error. It is very difficult to detect introgression and the DNA that is being assigned as Denisovan is probably ancient DNA indicative of ancient shared ancestry between humans, Denisovans and Neanderthals rather than genuine Denisovan DNA. The X-chromosome provides further insight into our ancient origins and intriguingly a haplotree constructed from part of the X-chromosome shows that the most recent common ancestor on our X-chromosome line traces back not to Africa but to Asia, and the TMRCA (time to the most recent common ancestor) is around two million years ago.

However, for genetic genealogists by far the most exciting part of Michael Hammer's talk was the story of the discovery of the new ancient root of the human Y-chromosome tree, which had first been announced to a select audience at the Family Tree DNA group administrators' conference in November 2012. The most extraordinary part of the story is that it was a citizen science discovery. An African American gentleman in South Carolina submitted a sample of his DNA to National Geographic's Genographic Project. He subsequently transferred his Y-DNA results to Family Tree DNA where he joined the haplogroup A project. Bonnie Schrack, the very astute administrator of the haplogroup A project, noticed that FTDNA had not been able to assign a haplogroup to the sample. She decided to take matters into her own hands and raised some money so that the Y-chromosome could be sequenced as part of the Walk through the Y programme run by Thomas Krahn, FTDNA's chief Y-chromosome scientist. It proved impossible to place the sequence on the Y-tree as all the SNP markers were ancestral, but there were also many new SNPs found in the sample. The challenge was then to determine precisely where the sample belonged on the tree as it fell outside the range of all known Y-chromosome lineages. Additional sequencing was done on chimps and gorillas for comparison purposes, and it was eventually determined that the sequence defined a new root of the Y-tree dating back around 338,000 years before present. The new root was given the name of haplogroup A00 leaving room for the possibility that additional divergent lineages might one day be discovered and it would then be a simple matter of adding additional zeros.

The research was published on 28th February in the American Journal of Human Genetics in an article entitled An African American Paternal Lineage Adds an Extremely Ancient Root to the Human Y Chromosome Phylogenetic Tree. The official press release from the University of Arizona can be read here. CeCe Moore, who attended the FTDNA conference, provides further details on her blog. The paper concludes with the following sentence: "Finally, the discovery of the A00 lineage demonstrates the power of public participation in the scientific process — a venture that is likely to continue in the current era of personal genomics." We have only captured a tiny fraction of the genetic diversity of the world at present. I wonder how many more exciting discoveries are waiting to be made as more people start to get their DNA tested and as more samples are tested from around the world and particularly in Africa. We can also expect many of these discoveries to be made by citizen scientists working as volunteer project administrators at commercial genetic genealogy testing companies.

There was so much going on at WDYTYA that unfortunately I did not have time to visit all the stands. I had wanted to ask Ancestry if they had any plans to launch their autosomal DNA test outside the US. Luckily David Hollister, a fellow member of the Guild of One-Name Studies, was able to have a word with them. He reported that they are not yet ready to launch their test outside the US for the following reasons:

David subsequently made further enquiries with Ancestry and was told by Karen Richardson, their Senior Manager for Community Marketing, that there is no definitive answer on the launch of the DNA test in the UK though "there is the hope that it might be in 2014, but we can't guarantee that".

The day ended at 4.30 pm, and it was then time to pack up the stands and head home. Max Blankfeld, FTDNA's Vice President of Marketing, had two enormous bags full of DNA swabs to take back with him to Houston, Texas. The company sold a record number of kits at WDYTYA this year. These samples are now starting to be processed. I have already had two new people join my Devon DNA Project who tested at WDYTYA, and I shall look forward to receiving their results in the next couple of months.

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The material on these pages is copyright Debbie Kennett or reproduced with permission from other copyright owners. It may be downloaded and printed for personal reference, but not otherwise copied, altered in any way or transmitted to others (unless explicitly stated otherwise) without the written permission of Debbie Kennett.